The present invention generally relates to tubing that is used to produce hydrocarbons in a subterranean environment and specifically to an improved tubing having an insert with electrical wiring.
Basic artificial lift methods to produce oil and water from a well have improved and changed in recent years. Nearly all methods of artificial lift still employ the connection of a plurality of pipes to form a conduit within a well that has been drilled and cased to allow oil and water to be pumped from the bottom of the well to production tanks at the surface. The production string usually has a pumping device at its lower end that is positioned near the bottom of the well bore that has been prepared for production. Pumping mechanisms such as electrical submersible pumps (ESP) and progressive cavity pumps (PCP) provide the energy needed to bring fluids to the surface through a string of jointed tubing. These pumps normally require an electric motor in order to make them work. Although a multitude of improvements have been made to these pumps over the years, there has been little done to reposition the wires that provide power to the pump from the outside of the tubing to the inside of the tubing.
For various reasons, those who are skilled in the science of producing fluids from a well have sought out a reliable method of supplying power to the bottom of a well bore. The previously proposed solutions to this problem have been unreliable, expensive, and complicated to install and remove. For example, the currently preferred method of power transmission to the bottom of the well bore is to secure a cable, that contains one or more wires by means of bands that secure the cable to the outside of the production string of tubing. The bands keep the wire adjacent to the tubing so that it does not snag on the production casing or on any objects which might be in the well bore. The bands also support the weight of the cable by securing the cable to the tubing. However, this method is problematic because it exposes the cable and bands to the corrosive elements of the well bore. Furthermore, installing (running) or removing (pulling) the tubing string creates opportunities to separate the cable from the tubing because inclined well bores (the most common type of well bores) increase the chance of the band to hanging up and failing at the gap where two joints of casing have been screwed together. Failure of one or more bands can prevent the removal of the pump or tubing because the annular space between the outside of the production tubing and the inside of the production casing is small and the cable, if not secured to the tubing, can wedge between the casing and the tubing causing the tubing to become stuck. Even if the cable does not break, the insulation on the wire inside the cable can be damaged which can create a short circuit in the electrical circuit, rendering the wire essentially useless. The tubing string then has to be pulled back up to the surface, and the short found and repaired, before the pump can be run back to bottom of the well bore. The problems created by banded external cables are costly and time consuming. Therefore, a need exists for an alternative method of power transmission from the surface to the bottom of the well bore that is both reliable and cost effective.
One solution to the above stated problem is to employ a plurality of tubing with multiple wires attached to the inside of the tubing instead of the outside of the drill pipe. While this solution alleviates the problem of snagging the wire, it does not solve the problem of exposing the wire to the harsh environment of the produced fluids that are contained within the production tubing. Simply hanging the cable on the inside of the tubing is also problematic because there is no way to support the weight of the cable and the pressure requirements of the pump will be higher due to the added friction between the fluid that is being pumped and the rough exterior of the cable.
Another solution to the above stated problem is to concentrically position the wires on the exterior of a tube that is inserted and attached to the actual production tubing itself. This solution avoids the problems presented by simply attaching the wire to either the interior or the exterior of the tubing. An example of this technique can be found in U.S. Pat. No. 4,683,944 (the ""944 patent) entitled xe2x80x9cDrill Pipes and Casings Utilizing Multi-Conduit Tubulars.xe2x80x9d The ""944 patent discloses a drill pipe with electrical wires positioned inside conduits in the drill pipe wall. However, positioning the wire inside the drill pipe wall significantly decreases the overall pipe wall thickness. In order to overcome the decreased wall thickness, significantly thicker drill pipes will have to be used. Furthermore, the multiple conduits create weak points in the drill pipe in between the conduits. The high rotational stress which the drill pipe encounters in the drilling operations can cause stress fractures in the pipe wall between the multiple conduit tubulars. In an extreme case, high rotational stress can lead to an internal fracture in the drill pipe that disengages the interior wall of the drill pipe from the exterior wall of the drill pipe.
Furthermore, the manufacture of the multiple conduit drill pipe is a complicated process which is unlike the manufacturing process for conventional drill pipe. Conventional drill pipe is manufactured by attaching male and female pipe connections to opposite ends of a conventional piece of pipe. The two connections are usually welded to the pipe. Multiple conduit pipes must be either extruded with the multiple conduits in place, or the multiple conduits must be drilled or cut out of a conventional drill pipe. In either case, the costs associated with manufacture of multiple conduit drill pipe are high.
Another problem encountered in the addition of wires to drill pipe, which is not unique to multiple conduits, is the problem associated with creating reliable, secure electrical connections. In conventional drill pipe the individual pipe segments screw together, creating a problem for connecting the wires during the screwing or unscrewing process. This problem can be overcome by using drill pipe that plugs together and that is secured with a threaded coupler. This type of connection is known in the art. The ""944 patent discloses a similar type of coupling connection, but requires a planer conduit seal in between the individual pipe segments in order to assure the integrity of the conduit connection. The removable conduit seal is crucial to the method in the ""944 patent because a permanently installed conduit seal would be susceptible to damage during manufacture, transportation, storage, and installation of the multiple conduit drill pipe during drilling operations. Installing these conduit seals during the drilling process is also a cumbersome and a time consuming process. Therefore, a need exists for a method of transmitting electrical power to the bottom of a well bore in which the electrical connections are adequately protected from damage and the process of connecting the individual pipe segments is relatively simple and fast.
The needs identified above exist for production tubing, drill pipe, casing, and/or for any cylindrical pipe used to produce hydrocarbons in a subterranean environment. Therefore, as used herein, the term xe2x80x9ctubingxe2x80x9d shall mean production tubing, drill pipe, casing, and/or any other cylindrical pipe that is used to produce hydrocarbons in a subterranean environment.
Since, the previous solutions to the power transmission problem are lacking, a need still exists for an apparatus and method of transmitting power to a well bore in which the wire is not exposed to either the interior or the exterior of the tubing and is operable with any conventional tubing, including without limitation production, casing or drill pipe. Furthermore, a need exists for an apparatus and method for connecting the individual tubing segments together in which the electrical connections are well protected and the connection process is quick and easy.
The present invention, which meets the needs stated above, is an improved tubing which overcomes the problems presented by earlier inventions involving tubing and electrical wiring combinations. The invention comprises a section of tubing with coupled end connectors and an insert containing at least one electrical wire. The insert has an outside diameter that is approximately equal to the inside diameter of the improved tubing. The insert also has projections at each end such that when two inserts are placed end to end, the projections will mate up. The insert has at least one groove cut into its side and running the length of the insert. The groove is for the placement of a wire for transmission of power to the well bore or for the placement of a wire for transmission of data from the well bore. The groove is installed down the length of the insert. The groove is deep enough so that when a wire is placed inside the groove, the wire does not project beyond the outside diameter of the insert. The insert may contain as many groove and wire combinations as are necessary for the particular application. The wire has an electrical connection at each end of the insert. When the inserts are placed end to end, the insert projections line up the electrical connectors and correct mating of the insert projections will result in correct mating of the electrical connectors.
The inserts, are the same length as the tubing and are installed inside the tubing such that the insert is flush with the first end of the tubing. The inserts are then welded to the tubing or secured to the tubing by some other method. A threaded coupler is then installed on the second end of the tubing to protect the exposed insert and electrical connector. The coupler will also be used to secure the improved tubing together.
Individual pieces of improved tubing are connected together in a three step process. First the coupler is threaded onto the second end of the tubing. Next, the first end of one tubing member is positioned above the second end of another tubing member. Next, the insert projections are properly aligned so that they will mate together. Then, the two pieces of tubing are plugged together so that the electrical connections engage each other. Finally, the coupler is screwed onto the first end of the tubing so that the two pieces of tubing are secured together. The process may be repeated as necessary to create an elongated string of improved tubing.